1. Field of the Invention
This invention relates to devices and methods for delivering therapeutic light to a tissue, and in particular to optical fiber arrangements in which a protective sheath is placed over the fiber prior to insertion into an endoscope that guides the fiber to a treatment site. The protective sheath prevents mechanical damage to working channel of the endoscope during insertion of the fiber, insulates the fiber from surrounding cooling fluids, protects the fiber when it is extended outside the scope, and may serve as an indicator of overheating that enables early detection of excess heating or burning of tissues or equipment at the treatment site. Preferably, the protective sheath is designed to be as thin as possible so that it does not impede flow of irrigation fluid to the treatment site or limit the flexibility of the fiber.
The material of the sheath is preferably selected to have a thermal signature that enables radiation emitted by the sheath as a result of overheating to be distinguished from radiation normally emitted during treatment. The thermal signature may, for example, be distinguishable by frequency domain analysis, rather than just by timing or amplitude, so as to ensure that detection of overheating is not affected by changes in radiation emitted during treatment due to changes in the tissue being treated, contact between the laser and the tissue (as frequently occurs during treatment of stones), or variations in the laser radiation applied to the treated tissue. In addition, the present invention may be used in connection with the inventor's Smart Fiber technology, in which a phosphor material is added to the fiber's buffer or cladding to provide light emission at a predetermined frequency/wavelength when too much errant laser energy is present and/or when overheating occurs, the sheath itself may include one or more phosphor materials that emit visible or infrared light at a particular frequency or wavelength in response to stimulation by temperature or radiation to provide an easily-observed indication of conditions at the treatment site, based on the color or frequency/wavelength of the light transmitted back to a surgeon or detection device at the input end of the scope, and/or such phosphor materials may be included in the catheter or introducer.
Additional features of the invention may include some or all of the following features: (a) trim markings at a distal end of a protective sheath, and/or provision of a cutting guide device, so that the protective sheath can easily be adapted for use with ureteroscopes and other endoscopes of different lengths; (b) arrangement of the sheath to glow if a fiber is pulled too far into the sheath, thereby providing a visual warning and protection for the scope is the fiber is pulled in too far, even when the field of view is otherwise cloudy due to the effects of the surgical procedure; (c) an arrangement and method of utilizing the protective sheath, in which liquid is drawn into the sheath by providing a tight fit between the outer diameter of the fiber and the inner diameter of the sheath that causes irrigation fluid to be drawn into the sheath as the fiber is pulled into the sheath; (d) modification of the fiber to include a ball or spherical tip with a flattened end; and (e) inclusion of perforations, apertures, or holes along the length of the sheath to improve sterilization efficiency.
2. Description of Related Art
It is known that protective sheaths may be used to protect the working channel of endoscopes and similar devices from damage caused during insertion of the fiber into the channel, and to provide an early warning that overheating is occurring by emitting radiation that has a different thermal signature than the radiation resulting from normal treatment. See, e.g., copending U.S. patent application Ser. No. 13/127,911, filed May 5, 2011 (based on PCT Appl. No. PCT/US2009/006021) and the article by R. W. Herrmann et al. entitled “Insertion Sheaths Prevent Breakage of Flexible Ureteroscopes Due to Laser Fiber Passage: A Video-Endouminal Study of the Working Channel,” Journal of Endourology, Vol. 24, No. 11, November 2010. In addition, see copending PCT Appl. No. PCT/US2009/006021, filed Nov. 6, 2009.
While such a sheath may provide good protection against mechanical damage to the scope or other instrument through which the fiber is inserted, however, the prior protective sheath designs have a number of disadvantages that have limited their applicability.
The first problem addressed by the present invention is that the previously proposed protective sheaths have the disadvantage that they impede flow of irrigation fluid past the sheath. While it has been proposed in the above-mentioned copending PCT Appl. No. PCT/US2009/006021 to reduce the wall thickness of the sheath, such reduction in the wall thickness of the sheath makes it difficult to detect emission of radiation from the sheath by conventional amplitude detection, especially in applications where the intensity of treatment radiation observed through the scope varies greatly due to changes in the tissue being treated and especially during contact between the fiber and the tissue. The Applicant has discovered that in may laser surgery procedures, such as urological stone removal, it is common for the fiber to actually contact the tissue, making it extremely difficult using conventional monitoring methods to distinguish emissions from the sheath itself that indicate overheating and potential damage to tissues or instruments.
The second problem addressed by the present invention is that endoscopic instruments, such as flexible ureteroscopes, have different lengths for different applications and patients. The need to manufacture, purchase, and stock scopes of different lengths has resulted in increased costs to both manufacturers and users. The present invention addresses this problem by permitting manufacture of the sheaths in one or just a few standard lengths, and providing trim markings to indicate proper lengths to enable the user to more easily trim the sheaths to the desired length using a cutting instrument such as a knife or scissors. Alternatively, the problem is addressed by providing a cutting guide that facilitates trimming of the sheaths to the appropriate lengths.
The third problem addressed by the present invention is that it is often difficult, due to debris obscuring the field of vision or excessive light from the glowing tissues or the laser itself, for a surgeon to determine the exact position of a laser-delivery fiber end relative to the scope. As a result, it is common for surgeons to pull the fiber tip slightly into the scope in order to the field of view, which can decrease the useful life of the fiber and present a danger of overheating. The present invention addresses this problem in two ways. The first is to improve visibility by arranging the sheath to glow during a treatment procedure, improving the visibility of the fiber tip so that it is not necessary to pull the tip into the scope for reference during treatment, and the second is to provide a tight fit between the sheath and the scope to cause a suction effect that draws cooling fluid into the sheath to help prevent overheating when the fiber is pulled a small distance into the sheath, whether intentionally or unintentionally.
The fourth problem addressed by the present invention relates to the use of spherical or ball shape fiber tips to enhance the protective effects of the fiber-length by facilitating insertion of the fiber/sheath combination into the endoscope, and by providing further protection from erosion of the fiber due to entry of reflected energy into the cladding and resultant overheating. The problem is that, in practice, it has been found that the spherical or ball-shaped fiber tip can itself be a source of overheating, caused by internal reflections within the fiber tip. The present application addresses this problem by modifying the spherical or ball-shaped fiber tip to include a flattened end. Preferably, the spherical or ball-shaped tip is formed first, and then the end of the sphere or ball shape is flattened to provide a hybrid spherical/chamfered structure.